Re: [PATCH 25/43] xfs: implement buffered writes to zoned RT devices

Christoph Hellwig
2025-02-14T06:22:57Z

On Thu, Feb 13, 2025 at 03:05:58PM -0800, Darrick J. Wong wrote:
> > we'll need a space allocation for every write in an out of tree write
> > file system. But -ENOSPC (or SIGBUS for the lovers of shared mmap
> > based I/O :)) on writes is very much expected. On truncate a lot less
> > so. In fact not dipping into the reserved pool here for example breaks
> > rocksdb workloads.
>
> It occurs to me that regular truncate-down on a shared block can also
> return ENOSPC if the filesystem is completely out of space. Though I
> guess in that case, at least df will say that nearly zero space is
> available, whereas for zoned storage we might have plenty of free space
> that simply isn't available right now... right?

That's part of it, yes as we can't kick GC. That reason will go away
if/when the VFS locking for truncates is fixed. But I also doubt people
run nasty workloads on reflinked files all that much.